Comparison of precursor neoplasms at colonoscopic diagnosis of early-onset and later-onset colon cancer.

Abstract

74 Background: Colorectal cancer (CRC) incidence has steadily increased in adults younger than 50 years (EO-CRC) since the 1990s, with a reported higher prevalence in the left colon and rectum. Established precursor lesions of CRCs are adenomas, including advanced adenomas, and sessile serrated polyps. We hypothesized that patients at diagnosis of early-onset colon cancer (EO-CC) would have fewer adenomas compared to patients with later-onset colon cancer (LO-CC). Methods: We performed a retrospective review of electronic health records and identified 58 patients diagnosed with EO-CC who had colonoscopy at Mayo Clinic or Mayo Health System who were then matched with 58 LO-CC patients based on gender and procedure indication (diagnostic in 76%, surveillance 16%, screening 8%)[2012 to 2021]. At colonoscopy where colon cancer was diagnosed, we recorded findings of adenomas, advanced adenomas (≥ 1 cm, villous histology, and/or high-grade dysplasia) and sessile serrated polyps. On CCs, limited molecular data were available [mismatch repair (MMR); BRAFV600E, KRAS]. Results: Among 116 patients included in the EO-CC and LO-CC study arms, the median age at cancer diagnosis were 42 and 74 years, respectively. No significant differences were found between study arms and risk factors for CRC including tobacco, alcohol, BMI, genetic syndromes, family history of CRC, and MMR, BRAFV600E or KRAS status (all p> 0.05). While no difference was found for polyp number by arm, patients with EO-CC had larger polyps (median of 10 mm vs 6 mm, p=0.001) compared with LO-CC. At least 1 adenoma was found in 50% and 52% of patients with EO-CC and LO-CC, respectively. Importantly, advanced adenomas were significantly more common in the EO-CC group compared with the LO-CC group (41% and 21%, p=0.027). Sidedness of all adenomas did not differ significantly for EO-CC vs LO-CCs. Conclusions: Patients found to have a primary EO-CC had a significantly higher likelihood of a synchronous advanced adenoma in the colon compared to those with a primary LO-CRC. Together, these data suggest accelerated carcinogenesis throughout the colorectum with increased risk of synchronous and metachronous patients with EO-CC. [Table: see text]